Platform Adaptation and Bring-Up
Jetson Nano Platform Adaptation and Bring-Up Guide DA_09361-002 | 9
Porting USB
Jetson Nano can support up to three SuperSpeed USB ports. In some implementations
not all of these ports can be used because of UPHY lane sharing among PCIE and XUSB.
The Jetson P3449 carrier board is designed and verified for one USB 3.0 port. If you
design your own carrier board, consult Jetson Nano Product Design Guide
to verify that
your board’s UPHY lane mapping is functionally compatible with that of P3449.
USB Structure
A SuperSpeed USB port has nine pins:
• VBUS
• GND
• D+/D−
• SSTX+/SSTX− (SuperSpeed data transmit)
• SSRX+/SSRX− (SuperSpeed data receive)
• GND_DRAIN for drain wire termination and managing EMI, RFI, and signal
integrity
The D+/D− signal pins connect to UTMI pads. The SSTX/SSRX signal pins connect to
UPHY and are handled by a single UPHY lane. As UPHY lanes are shared between
PCIE and XUSB, UPHY lanes must be assigned according to the custom carrier board’s
requirements.
UPHY Lane Assignment
Universal Physical Layer (UPHY) is a physical I/O interface layer that can serve multiple
types of interfaces, e.g. USB and PCIe. A single UPHY lane can support multiple types of
interfaces.
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